Engine starter gearing



April 1955 c. A. MENDENHALL ENGINE STARTER GEARING 2 Shegts-Sheet 1Filed April 17, 1952 W TTOHNE Y III . INVENTOR.

. 2/ BY WITNESS:

p l 9, 1955 A. MENDENHALL v2,706,413

ENGINE STARTER GEARING Filed April 17, 1952 2 Sheets-Shes} 2 IN V ENTOR.

wnwsss; y )f 04 Agi f member in spaced relation United States PatentENGINE STARTER GEARING Charles A. Mendenhall, Elmira, N. Y., assignor toBendix Aviation Corporation, a corporation of Delaware Application April17, 1952, Serial No. 282,847

Claims. (Cl. 74-7) The present invention relates to engine startergearing and more particularly to a heavy duty drive of the automaticallyengaging type which is arranged to maintain its driving connection untilthe engine is reliably selfoperative.

It is an object of the present invention to provide a novel starterdrive of the above type incorporating a yielding connection which isadapted to overrun when the engine fires and accelerates the pinion.

It is another object to provide such a device in which the overrunningcoupling is adapted to absorb shock loads without generating undesirablysevere stresses in the coupling parts.

It is another object to provide such a device incorporating separateyielding means to insure proper mesh of the pinion with the engine gearwhen the starting motor is energized.

It is another object of the present invention to provide such a devicein which the yielding driving connection is coupled directly to thepinion, thereby minimizing the shock load on the parts at the initiationof the cranking operation.

Further objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawing in which:

Fig. l is a side elevation partly broken away and in section of apreferred embodiment of the invention.

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1;

Fig. 3 is a view similar to Fig. 2 showing the positions of the partswhen the drive is subjected to the cranking load;

Fig. 4 is a view similar to Fig. 2 showing the yielding coupling withthe parts in the positions assumed during overrunning of the connection;

Fig. 5 is a side elevation partly in section of a second embodiment ofthe invention; and

Fig. 6 is a section taken substantially on the line 66 of Fig. 5.

In Fig. 1 of the drawing there is illustrated a power shaft 1 on which ascrew shaft 2 is slidably journaled. A pinion 3 is threaded on the screwshaft for movement into and out of mesh with an engine gear 4, themeshing position of the pinion being defined by a stop nut 5 threaded onthe end of the screw shaft.

The screw shaft 2 is formed with a driven coupling member 6, and ahollow cylindrical driving coupling member 7 is rigidly mounted on thepower shaft 1 as indicated at 8, in position to surround thedrivencoupling thereto, the inclosure of the members being preferablycompleted by a cover coupling driving coupling member by plate 9retained in the lock rings 11, 12.

Yield-ing means for transmitting rotation from the driving member 7 tothe driven member 6 is provided in the form of a plurality of springblades 13 each of which bears at one end against a longitudinallyextending driving shoulder 14 on the inner surface of member 7, and atits other end on a ratchet tooth 15 formed on the driven member 6. Thespring members 13 are preferably, though not necessarily, of laminatedconstruction as shown, and transmit torque to the driven member byendwise compression. Suitable means such as flexible pins 16 areprovided for holding the outer ends of the blades 13 against theshoulders 14 with freedom for pivotal movement, and springs 17 seatedagainst the interior of the coupling member 7 serve to yieldingly pressthe inner 2,706,413 Patented Apr. 19, 1955 ends of the blades 13 intoengagement with the ratchet teeth 15.

The overrunning coupling provided by the blades 13 and ratchet teeth 15,is longitudinally slidable and a thrust spring 18 is located on thepower shaft bearing in a recess 19 in the end of the screw shaft andnormally holding the driven coupling member 6 in engagement with thecover plate 9.

A centrifugal latch member 21 is mounted in an extension 22 of thepinion 3 with freedom for radial movement against the pressure of alatch spring 23 which normally presses the latch into frictionalengagement with the screw shaft 2. The screw shaft is provided with adepression forming a shoulder 24 so located thereon that the latchenters the depression shortly before the pinion enters fully into meshwith the engine gear 4. The engagement of the latch with the shouldertherefore prevents the pinion from moving out of mesh with the enginegear until the rotation of the pinion becomes sufliciently rapid toWithdraw the latch from its engagement with the screw shaft.

In the operation of this embodiment of the invention, starting with theparts in the positions shown in Fig. 1, rotation of the power shaft bythe starting motor, not illustrated, is transmitted through the couplingmembers to the screw shaft whereby the pinion is traversed into meshwith the engine gear. When the travel of the pinion is arrested by thestop nut 5, the pinion is forced to rotate with the screw shaft, andtorque is transmitted to the screw shaft yieldingly by virtue of theelasticity of the blades 13, as shown in Fig. 3.

When the engine fires, the acceleration of the pinion by the engine gearis initially transmitted to the screw shaft by the engagement of thelatch 21 of the pinion with the shoulder 24 of the screw shaft. Thedriven coupling member 6 is thus caused to overrun the driving couplingmember 7 as shown in Fig. 4. When the speed of the pinion reaches thecritical point, the latch 21 is withdrawn by centrifugal force, and thepinion permitted to return to idle position, its motion being preferablycushioned by a rebound check spring 25.

In the embodiment illustrated in Figs. 5 and 6 a power shaft 31 hasfixed thereon in any suitable manner as indicated at 32 a driving memberin the form of a cylindrical housing 33 having drive lugs or shoulders34 formed in the interior thereof. A combined pinion and screw shaftmember 35 is slidably journaled on the power shaft 31 for longitudinalmovement into and out of mesh with an engine gear 36, and is normallymaintained in idle position by an anti-drift spring 37 which bearsagainst the frame of the starting motor 38. A nut member 39 is threadedon the pinion-screw shaft 35 confined between the flanges 41, 42 of thedriving member 33 and is provided with a plurality of ratchet teeth 43corresponding in number to the shoulders 34 of the driving member.

Means for yieldingly transmitting rotation from the driving member 33 tothe nut member 39 is provided in the form of spring blades 44 seated attheir ends against the shoulders 34 and teeth 43 of the drive member andnut respectively, the driving ends being retained against the shoulders44 by suitable means such as a wire stirrup 45, and the opposite endsbeing yieldingly pressed against the nut member by means of springs 46.

In the operation of this embodiment of the invention, rotation of thepower shaft 31 by the starting motor 38 is transmitted through thedriving member 33 and elastic blade members 44 to the nut member 39.Rotation of this nut member causes the pinion-screw shaft 35 to betraversed to the right in Fig. 5 so as to bring the pinion into meshwith the engine gear 36, the meshing movement being limited by theengagement of the shoulder 47 of the screw shaft with the flange 42 ofthe driving member 33. The pinion 35 is then caused to rotate with thepower shaft 31, the driving force being cushioned by the elasticity ofthe spring blades 44 whichin yielding absorb the shock loads.

When the engine starts, the acceleration of the engine gear 36 causesthe pinion 35 to thread itself back in the nut member 39 and return toits idle position where it is yieldingly retained by the anti-driftspring 37, the inertia of the parts being dissipated by overrunning thedriving member 33, as permitted by the ratchet formation of teeth 43.

Although but two embodiments of the invention have been shown anddescribed in detail, it will be understood that other embodiments arepossible and changes may be made in the design and arrangement of partswithout departing from the spirit of the invention.

I claim:

1. In an engine starter drive a driving member in the form of a hollowcylinder having a plurality of internal longitudinally extendingshoulders, a driven member concentric therewith =in spaced relationthereto having a plurality of longitudinally extending ratchet teethcorresponding to the shoulders of the driving member, spring bladesbearing at their ends against the shoulders of the driving member andteeth of the driven member respectively, a pinion, and means actuated bythe driven member for moving the pinion into mesh with a gear of theengine to be started, and for thereafter connecting the pinionpositively to rotate with the driven member and crank the engine.

2. An engine starter drive as set forth in claim 1, including furthermeans for pivotally connecting the outer ends of the spring blades tothe interior of the driving member, and means for yieldingly pressingthe inner ends of said blades into engagement with the teeth of thedriven member.

3. In an engine starter drive a power shaft, a screw shaft slidablyjournaled thereon, a pinion threaded on the screw shaft for longitudinalmovement into and out of mesh with a gear of the engine to be started, astop on the power shaft defining the operative position of the pinion,said screw shaft having a driven coupling member formed thereon, adriving coupling member enclosing the driven coupling member, and meansincluding a plurality of flexible spring blades connecting the couplingmembers and transmitting torque from the driving memher to the drivenmember by endwise compression; in which the driving coupling member isformed with abutments pivotally receiving the outer ends of the springblades, and the driven coupling member is provided with ratchet teeth;and including further means for yieldingly pressing the inner ends ofthe spring blades against the driven coupling member.

4. In an engine starter drive a power shaft, a screw shaft slidablyjournaled thereon, a pinion threaded on the screw shaft for longitudinalmovement into and out of mesh with a gear of the engine to be started, astop on the power shaft defining the operative position of the pinion,said screw shaft having a driven coupling member formed thereon, adriving coupling member enclosing the driven coupling members, and meansincluding a plurality of flexible spring blades connecting the couplingmembers and transmitting torque from the driving member to the drivenmember by endwise compression, in which the coupling members arelongitudinally slidable with respect to each other; and includingfurther yielding means for pressing the screw shaft against the stop onthe power shaft.

5. In an engine starter drive a power shaft, a screw shaft slidablyjournaled thereon, a pinion threaded on the screw shaft for longitudinalmovement into and out of mesh with a gear of the engine to be started, astop on the power shaft defining the operative position of the pinion,said screw shaft having a driven coupling member formed thereon, adriving coupling member enclosing the driven coupling member, and meansincluding a plurality of flexible spring blades connecting the couplingmembers and transmitting torque from the driving member to the drivenmember by endwise compression; in which the driven member is formed as aratchet having teeth with which the ends of the spring blades engage;including further means for holding the pinion in mesh with the enginegear until the pinion attains a predetermined rotative speed, aspermitted by the ratchet connection between the spring blades and thedriven member.

References Cited in the file of this patent UNITED STATES PATENTS1,210,028 Adams Dec. 26, 1916 2,021,921 Osterholm Nov. 26, 19352,166,014 McManens July 11, 1939

